feat: delete ticker from database when removed from portfolio

- Add DELETE support to /api/stocks endpoint via _method parameter
- Modify removeStock to delete db- prefixed entries from database
- Add confirmation dialog on delete button click
- Add test for stock deletion

app/routes/api/stocks/index.ts

@@ -10,11 +10,19 @@ export async function loader() {
 export async function action({ request }: { request: Request }) {
   const formData = await request.formData();
   const ticker = formData.get("ticker")?.toString().toUpperCase();
+  const method = formData.get("_method")?.toString() || "POST";
 
   if (!ticker) {
     return Response.json({ error: "Ticker is required" }, { status: 400 });
   }
 
+  if (method === "DELETE") {
+    await db.stock.deleteMany({
+      where: { ticker },
+    });
+    return Response.json({ success: true });
+  }
+
   const stock = await db.stock.create({
     data: { ticker },
   });